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GitLabApplication

CVE-2021-39939

MEDIUM · 6.5 CVSS v3.1 Published 2021-12-13
Fix available
A fix is available. Upgrade to 14.3.6 / 14.4.4 or later.
See remediation →
71/100
Remediation priority · Elevated
Remotely reachable Zero-click

Official description Straight from the sourceThe vendor's or NVD's own wording, published unedited. Authoritative, but often terse — it says what broke, rarely what to do.

NVD · unedited
An uncontrolled resource consumption vulnerability in GitLab Runner affecting all versions starting from 13.7 before 14.3.6, all versions starting from 14.4 before 14.4.4, all versions starting from 14.5 before 14.5.2, allows an attacker triggering a job with a specially crafted docker image to exhaust resources on runner manager

Technical summary Written by usOur analysis, written from the advisory, the CVSS vector and the affected-version data. It adds context the advisory leaves out, and never invents facts that are not in the source.

dbcve analysis · high confidence

GitLab Runner versions prior to 14.3.6, 14.4.4, and 14.5.2 contain an uncontrolled resource consumption vulnerability where a specially crafted docker image in a job can exhaust resources on the runner manager, potentially causing denial of service.

MitigationUpgrade GitLab Runner to version 14.3.6, 14.4.4, 14.5.2 or later. Alternatively, implement job resource limits and timeout configurations in the runner's config.toml to constrain job resource usage.

Verify against the referenced sources before acting — the references below are authoritative for this CVE, this summary is not.

Affected products & versions What the vendor confirmedThe version ranges the vendor confirmed as vulnerable. If your version sits inside a range here, treat yourself as exposed until you have upgraded.

NVD · CPE data
GitLabApplication
Affected:>= 13.7.0, < 14.3.6>= 14.4.0, < 14.4.4>= 14.5.0, < 14.5.2

CVSS breakdown How the score is builtThe industry scoring standard. It rates how the flaw is reached, what it takes to exploit, and what an attacker gains — the score is derived from those, not the other way round.

From the vector
Attack vector
Network
Complexity
Low
Privileges
Low
User interaction
None
Scope
Unchanged
Confidentiality
None
Integrity
None
Availability
High

CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H

Am I affected? How to checkSteps we derive from the advisory and the affected-version data, so you can decide whether this CVE reaches your setup. They are a guide, not a scan — your own configuration is the authority.

dbcve checks

Work through these to decide whether this CVE applies to you.

  1. Determine GitLab Runner version
    Run 'gitlab-runner --version' on the runner host to retrieve the installed version number
    Affected if The version shown is 13.7.0 to 14.3.5, 14.4.0 to 14.4.3, or 14.5.0 to 14.5.1 (all versions prior to 14.3.6, 14.4.4, and 14.5.2 in the listed ranges)
  2. Confirm Docker executor is configured
    Inspect the runner's config.toml file (typically at /etc/gitlab-runner/config.toml) and locate the [[runners]] sections to check for 'executor = "docker"'
    Affected if Docker executor is enabled, as the vulnerability is triggered by specially crafted docker images in jobs
  3. Check if job resource limits are defined
    Review the config.toml file for any 'limit' parameter under [[runners]] or 'docker' section, or check .gitlab-ci.yml for 'cpu', 'memory', or 'timeout' settings
    Affected if No resource limits (such as memory limits, CPU limits, or job timeouts) are configured in either the runner config or the CI/CD pipeline definitions

You are affected if your GitLab Runner version falls within the vulnerable ranges (13.7.0 to 14.3.5, 14.4.0 to 14.4.3, or 14.5.0 to 14.5.1) AND the Docker executor is in use, with no resource limits configured to constrain job consumption.

Generated from the published advisory. Verify against your own configuration.

Check your environment

Paste your version and any relevant configuration and it will be compared against the affected criteria above. Do not include secrets or credentials.

AI-assisted, checked against the advisory. Informational, not a guarantee.

Remediation Closing itWhat it takes to close this. Where a vendor fix exists we point at it; where none exists we say so plainly, and can build one. Effort estimates are scoped from the advisory, not from your codebase.

dbcve · scoped
Upgrade available Upgrade to 14.3.6 / 14.4.4 / 14.5.2 or later
Fixed in 14.3.614.4.414.5.2
Interim mitigation

Upgrade GitLab Runner to version 14.3.6, 14.4.4, 14.5.2 or later. Alternatively, implement job resource limits and timeout configurations in the runner's config.toml to constrain job resource usage.

Recommended fix High confidence

14.3.6, 14.4.4, or 14.5.2 depending on current version branch

  1. Identify the currently running GitLab Runner version using `gitlab-runner --version`
  2. Determine which version branch you are on (13.7.x, 14.3.x, 14.4.x, or 14.5.x)
  3. Stop the GitLab Runner service using `sudo gitlab-runner stop` or `systemctl stop gitlab-runner`
  4. Upgrade GitLab Runner to the appropriate fixed version: for 13.7.x upgrade to 14.3.6; for 14.4.x upgrade to 14.4.4; for 14.5.x upgrade to 14.5.2
  5. Verify the installed version with `gitlab-runner --version`
  6. Start the GitLab Runner service using `sudo gitlab-runner start` or `systemctl start gitlab-runner`

Generated from the published advisory — verify against the referenced sources before acting.

Fix this in GitLab Scoped from the published advisory
  • Consultation1.0 h
  • Implementation2.0 h
  • Testing2.0 h
  • Review / QA1.0 h
6.0 hours of engineering $1,040
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References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.

Primary sources

Practitioner notes

Contributed

Peer-ranked notes from engineers who’ve handled CVE-2021-39939 in production — separate from our analysis above.

No notes yet

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What this is

A place for practitioners to share what actually worked: a mitigation you’ve tested, a configuration change, a version- or environment-specific caveat, or a link to a verified patch. The most useful notes rise to the top as peers upvote them, so the signal stays high.

What belongs here
  • Verified mitigations, workarounds, and config changes
  • Version or environment caveats, and links to real fixes
  • No weaponised exploit code, or anything meant to cause harm
  • No spam, self-promotion, credentials, or personal data